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1. Field of the Invention
The present invention relates to a system displaying visual images in sequences generated by user-interactivity. In particular, the present invention provides for generating a sequence of visual images in response to the position of an object.
2. Description of Related Art
Motion pictures, or movies, consist of sequences of images related to one another by chronological order, the difference between each frame being an incremental change over time of the subject of the movie. Movies typically are stored in a medium such as film, video tape, or optical video disc as a library of pre-defined frames of image data. The viewer passively views the movie, having no ability to control the sequence of images presented. The existing technologies have evolved, therefore, to display movies in predefined time-based order providing the viewer with no control over the sequence of frames displayed.
Display technologies have developed to provide for speeding up, slowing down or stopping the motion of a movie by changing the speed of access of new visual images from the storage medium. This type of user control virtually speeds up, slows down or stops time in the movie, but does not change the sequence of visual images displayed. In addition, to the standard speed control on video display systems, some video machines provide "jog controls" which allow a user to step through the images in a movie one frame at a time.
User interactive systems such as the movie map have been developed, but have had limited success in providing user input for controlling the sequence of images that creates a feeling of real time interaction. Examples of the movie map include the Aspen, Colorado project which is described in a doctoral thesis entitled "Cognitive Space in the Interactive Movie Map: An Investigation of Spatial Learning in Virtual Environments", by Robert Mohl, 1981, submitted at the Massachusetts Institute of Technology. In addition, applicant is aware of movie maps which have been created of Paris, France for exhibition by the Paris Metro, and of the Polenque ruins in Mexico, funded by RCA and done by the Bank Street College of New York City. In each of these movie map systems, the user is provided with control switches to adjust the apparent speed of motion along displayed streets or pathways filmed at real places. Further, the system provides for the ability to go forward or backward down the streets. At intersections, the user can select a direction in order to turn left or right. These movie maps give the user control over the direction and rate of apparent motion through the places represented by the library of video frames provided using a joystick or buttons to control display mode on video optical disc players. The Aspen movie map gives the user a map of Aspen and an indicator which locates the displayed frame on the map to provide a "you are here" effect.
Other systems using rate and direction input to traverse a library of video frames include simulators such as vehicle flying or driving simulators.
Another prior art form of interactive video display similar to the movie map is described in the master's thesis entitled "Viewpoint Dependent Imaging: An Interactive Stereoscopic Display", by Scott Fisher, submitted to the Massachusetts Institute of Technology, 1981. The viewpoint-dependent imaging system tracks the position of a viewer's head to control the display of images. The images are organized in sequences to mimic changes in perspective correlating with motions of the viewer's head as constrained by the stored sequences. As the viewer's head moves with respect to the display screen, the image on the display changes to reflect the changing viewpoint. In practice, the viewpoint-dependent imaging system actually uses detected position of the viewers' head to control the rate and sequence of frame access to traverse the stored sequences to a frame matching the viewer's actual position. Because of the discrete rates of frame access, there is a decoupling effect between the motion of the viewer's head and the actual images displayed. Unlike the driver of a real car who, when he turns the steering wheel causes the car to turn instantly, the image in discrete rate-dependent interactivity systems lags the user inputs or does not match them. Thus, when the user stops, the visual image continues to change for a perceptible interval until the image displayed catches up with the actual detected position of the viewer's head. Another decoupling effect arises because the stored images are created based on a pre-selected set of perspectives and the viewer's head will only rarely be located precisely at a position corresponding to one of the perspectives, and because the image is limited to prefilmed perspectives. Thus, to the extent that the viewer's head is not located at a position having a corresponding stored image, a perceptible skew is observed in the alignment of the displayed sequence of images with the real position of the viewer's head. These decoupling effects cause the interactivity to feel artificial to the user. In order to overcome these and other problems, recent viewpoint-dependent systems have used computer generated graphics. See S. S. Fisher, et al., "Virtual Environment Display System", ACM 1986 Workshop on Interactive 3D Graphics, Oct. 23-24, 1986, Chapel Hill, N.C.
Other interactive display systems have been created using computer-generated graphics. For instance, a graphic designer for an automobile can display interactively several viewpoints of the automobile being designed using keyboard control. However, in such computer-generated graphic systems, the entire, or a substantial amount of the graphic image is re-calculated during each frame update to present the change of perspective. There is no large library of video frames that is traversed in response to the user inputs. These prior art computer-generated graphic systems provide powerful user interactivity but require powerful, fast computers which are beyond the reach of most users. Further, to provide quality video images, comparable to those obtainable by pre-created frames of video data or images created by video camera and stored on a medium such as optical video disc, the quantity of data to be re-calculated for each frame is prohibitive.